The present invention relates to a liquid-cooled engine of the vertical shaft type provided with water jackets communicating the periphery of each cylinder of the engine with the interior of the respective cylinder head thereof
In a prior art engine of the horizontal shaft type, there has been proposed an engine such as disclosed in Japanese Utility Model Laid-Open No. 73515/80. However, difficulties arise when such an engine of the horizontal shaft type is adapted as an engine of the vertical shaft type without changing the construction thereof, in that the thermostat chamber projects upwardly beyond the cylinder so that the total height of the engine becomes too great.
Particularly, in the case where a radiator is arranged in a position above the engine, the radiator must be located at a very high position because of the necessity of providing piping therefor, thereby making the piping and assembling of the radiator very difficult.
The prior art of liquid-cooled engines of the vertical shaft type has been directed to mainly outboard engine applications. Such a prior art engine is shown in FIG. 2 of Japanese Patent Laid-Open No. 49120/85.
In such a prior art engine, an exhaust valve thereof is arranged at an upper position in the engine, while an intake valve is located at a lower position thereof, and, as a result, the following defects occur:
Immediately after the start of the engine, when the termostat valve is closed, the cooling water in the water jacket is generally heated by the convection of the cooling water. However, when a high temperature portion of the engine, such as an exhaust valve, is located at a higher position, a large temperature difference will develop between a higher portion and lower portion of the water jacket delaying the heating of air drawn into the engine.
Further, water can not flow smoothly around the exhaust valve and the exhaust passage which require the largest cooling effect, thereby deteriorating the cooling effectiness.